The others are Altran, Hexion and Momentive and there are more but they do not want to become famous for this or will not be mentioned for security reasons.
This attack could be potentially dangerous for both machines and personnel so Hydro shut down their computers and ran the production manually.
So far this has cost them about 35 Million Euro! So in terms money this is severe.
For this attack to work it needs a Windows system:
It's not clear how the LockerGoga hackers are gaining initial access to victim networks in those targeted cases, but Carmakal has found that they seem to already know targets' credentials at the start of an intrusion, perhaps thanks to phishing attacks or by simply buying them from other hackers. Once the intruders have an initial foothold, they use the common hacking toolkits Metasploit and Cobalt Strike to move to other computers on the network and also exploit the program Mimikatz, which can pull traces of passwords out of the memory of Windows machines and allow them to gain access to more privileged accounts.
Once the privileges of Windows are gathered the encryption can follow. For this they need the domain admin credentials.
They use the Microsoft's Active Directory management tools to plant their ransomware payload on target machines across the victim's systems. For this they use a false certificate.
This will make the system toast within minutes and you will find a README file that states:
Greetings! There was a significant flaw in the security system of your company, You should be thankful the flaw was exploited by serious people and not by some rookies. They would have damaged all your data by mistake or for fun.
It is debatable how serious these people are because they destroy the computers to a degree that it will be hard to even pay ransom.
There is however good reason to believe the first part of the message. There must have been a significant flaw in the security system...besides Windows
It seems very much safer to use a Linux network and Linux servers...and Linux desktops.